I recently upgraded to this version 27.8.3 (64-bit) and the two-page login has stopped putting my saved Password into the second page. Nothing has changed regarding Add-ons, I just used the Linux Installer/Updater.

It puts in the login name OK, but then the next page for Password, I have to go to the Saved passwords and get the Password and paste it in.

Firefox Works OK for two-page login, so pretty sure it is not a website-thing.